Plasma kallikrein (pKal) is the primary bradykinin-generating enzyme in the circulation. The activation of pKal occurs via the contact system which has been linked to disease pathology associated with hereditary angioedema (HAE). Bradykinin is a key mediator of pain, inflammation, edema and angiogenesis.
Plasma protease C1 inhibitor (also known as C1-inhibitor or C1-INH) is a protease inhibitor belonging to the serpin superfamily. Its main function is the inhibition of the complement system to prevent spontaneous activation. Hereditary angioedema types I and II are caused by genetic deficiencies of C1-INH, which lead to overproduction of bradykinin.